Recent Advances of Landfill Leachate Treatment

Landfill leachate poses significant risks to the environment and human health if not managed properly due to its potential to contaminate soil, ground, and surface waters. Consequently, effluent standards for landfill leachate have been continuously reviewed to manage these risks. A combination of treatment techniques (e.g., physico-chemical and biological) are usually required to treat landfill leachate due to its complexity, variability, and potentially high concentrations of pollutants. This review considers the various types of techniques used to treat landfill leachate/leachate concentrate, including advanced oxidation process (AOP), membrane bioreactor, denitrification, biofilm reactors, and electrocoagulation. The occurrence and treatment of emerging contaminants in landfill leachate, and opportunities for development are also considered. The review covers the basic principles through to the latest developments in research, including the effectiveness of engineering applications, their economic and technical challenges, together with current gaps in the knowledge and the prospects for leachate treatment. A systematic review of the technical characteristics of the engineering applications, used in leachate membrane concentrate treatment, showed that low-energy direct heat transfer evaporation technology had good prospects for future development. Refractory organic compounds, high concentrations of ammonia, high salinity, and concentrated leachate were of high concern. Hence, extensive research has been conducted on the degradation of refractory organic compounds using various AOPs, and the denitrification of ammonia species by novel biological pathways (e.g., anaerobic ammonium oxidation, short-cut denitrification processes). Despite the significant number of promising laboratory scale applications, further research is needed to demonstrate their effectiveness on a commercial/large scale.